Re: [PATCH v22 3/3] virtio-balloon: don't report free pages when page poisoning is enabled
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2018-01-18 22:37:36
Also in:
kvm, linux-mm, lkml
On Wed, Jan 17, 2018 at 01:10:12PM +0800, Wei Wang wrote:
The guest free pages should not be discarded by the live migration thread when page poisoning is enabled with PAGE_POISONING_NO_SANITY=n, because skipping the transfer of such poisoned free pages will trigger false positive when new pages are allocated and checked on the destination. This patch adds a config field, poison_val. Guest writes to the config field to tell the host about the poisoning value. The value will be 0 in the following cases: 1) PAGE_POISONING_NO_SANITY is enabled; 2) page poisoning is disabled; or 3) PAGE_POISONING_ZERO is enabled. Signed-off-by: Wei Wang <redacted> Suggested-by: Michael S. Tsirkin <mst@redhat.com> Cc: Michal Hocko <mhocko@suse.com>
Pls squash with the previous patch. It's not nice to break a config, then fix it up later.
quoted hunk
--- drivers/virtio/virtio_balloon.c | 8 ++++++++ include/uapi/linux/virtio_balloon.h | 2 ++ 2 files changed, 10 insertions(+)diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index b9561a5..5a42235 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c@@ -706,6 +706,7 @@ static struct file_system_type balloon_fs = { static int virtballoon_probe(struct virtio_device *vdev) { struct virtio_balloon *vb; + __u32 poison_val; int err; if (!vdev->config->get) {@@ -740,6 +741,13 @@ static int virtballoon_probe(struct virtio_device *vdev) WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0); INIT_WORK(&vb->report_free_page_work, report_free_page_func); vb->stop_cmd_id = VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID; + if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) || + !page_poisoning_enabled()) + poison_val = 0; + else + poison_val = PAGE_POISON; + virtio_cwrite(vb->vdev, struct virtio_balloon_config, + poison_val, &poison_val); } vb->nb.notifier_call = virtballoon_oom_notify;diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h index 55e2456..5861876 100644 --- a/include/uapi/linux/virtio_balloon.h +++ b/include/uapi/linux/virtio_balloon.h@@ -47,6 +47,8 @@ struct virtio_balloon_config { __u32 actual; /* Free page report command id, readonly by guest */ __u32 free_page_report_cmd_id; + /* Stores PAGE_POISON if page poisoning with sanity check is in use */ + __u32 poison_val; }; #define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */-- 2.7.4